Mineral prospectivity mapping constitutes an efficient tool for delineating areas of highest interest to guide future exploration. Multiple knowledge-driven approaches have been applied for the creation of prospectivity maps for deep-sea ferromanganese (Fe-Mn) crusts over the last decades. The results of a data-driven approach making use of an extensive data collection exercise on occurrences of Fe-Mn crusts in the World Ocean and recent increase in global marine datasets are presented. A Random Forest machine learning algorithm is applied, and results compared with previously established expert-driven maps. Optimal predictive conditions for the algorithm are observed for (i) a forest size superior to a hundred trees, (ii) a training dataset larger than 10%, and (iii) a number of predictors to be used as nodes superior to two. The confusion matrix and out-of-bag errors on the remaining unused data highlight excellent predictive capabilities of the trained model with a prediction accuracy for Fe-Mn crusts of 87.2% and 98.2% for non-crusts locations, with a Kohen’s K index of 0.84, validating its application for prediction at the World scale. The slope of the seafloor, sediment thickness, sediment type, biological productivity, and abyssal mountain constitute the five strongest explanatory variables in predicting the occurrence of Fe-Mn crusts. Most ‘hand-drawn’ knowledge-driven prospective areas are also considered prospective by the random forest algorithm with notable exceptions along the coast of the American continent. However, poor correlation is observed with knowledge-driven GIS-based criterion mapping as the Random Forest considers un-prospective most target areas from the GIS approach. Overall, the Random Forest prediction performs better in predicting a high chance of Fe-Mn crust occurrence in ISA licensed area than the GIS approach, which constitutes an external validation of the predictive quality of the random forest model.

The Tellus stream sediment and deep soil geochemistry data sets for Northern Ireland were used to locate four types of critical metals anomalies in granite bedrocks of the Mourne Mountains. A curvi-linear array of Nb, REE, Th and U soil anomalies across the eastern Mourne Mountains correlated with late-stage and eutectic temperature minerals in the roof zone of the most peralkaline F- and volatile-rich granite body, remobilized on micron to millimetre scales. Li, Be, B, As, Sn, Mn 3+ and Ce 4+ partitioned into pockets of late-stage heterogeneously distributed F-rich silicic residual melts and relatively oxidizing halide-rich magmatic fluids, resulting in drusy mineral and hydrothermal assemblages. Isolated soil anomalies correlated with amorphous Mn 3+ - and Ce 4+ -rich masses infilling drusy cavities, which resulted from short-distance percolation of small volumes of late-stage magmatic fluids. A significant As plume in stream sediments emanated from a greisen that hosted multiple critical and base metals including Sn, from reactions between large volumes of magmatic As + halide-rich fluids and mafic silicate + diverse accessory minerals on the metre- to kilometre-scale along geological structures. Diverse, small-scale REE anomalies in the soil data along structural features in the western Mournes correlate with vein mineralization resulting from episodic migration of hydrous fluids of variable composition, probably with a much smaller magmatic component than elsewhere. The regional geochemical dataset proved useful to develop a multi-stage model for enrichment of critical metals in the Mourne Mountains granites, which is analogous to the petrogenesis of some of the igneous-hosted economic deposits of critical metals. Thematic collection: This article is part of the energy-critical metals for a low carbon transition collection available at: https://www.lyellcollection.org/topic/collections/critical-metals

We present enigmatic toroidal carbonate concretions retrieved from 700 m water depth from two sites in the upper plateau of the Rio Grande Rise. The concretions have a diameter of similar to 15 cm and a central hole of similar to 5 cm, and were observed on top of loose bioclastic sand over an area of similar to 30 m(2) at 0.5-1.5 m from one another. They consist of brown, porous, bioclastic grainstone, lacking internal structures. Grains consist of sand (< 3% coarse, 30% medium, 35% fine, 25% very fine), composed mainly by planktonic foraminiferal tests, and < 10% lime mud. The observed foraminiferal species indicate initial deposition of the sand in an open ocean setting. Biostratigraphy suggests an age no older than Pleistocene. Petrographic thin sections and SEM reveal that the fossiliferous grainstone contains intraclastic micritic cement and isopachous rim cement made of bladed magnesian calcite. delta O-18 values range from +1.5 to +3.3 parts per thousand (V-PDB) and increase with the degree of cementation, while delta C-13 ranges from +0.5 to +2.3 parts per thousand irrespective of cementation. The cementation of the grainstones is likely to have taken place in the marine phreatic environment. Carbonate precipitation induced by methane oxidation or (subaerial) meteoric diagenesis are ruled out based on both cement fabric and isotopic composition. Plausible causes for the toroidal shape of these structures could be: 1) sediment excavation by organisms, or 2) cementation within biofilms around burrows, followed by selective seafloor erosion. However, unveiling the actual formation mechanisms warrants further investigation.

The ocean dominates the Earth's surface, but despite decades of exploration it remains poorly explored, with major geological, oceanographic and biological discoveries frequently being made. The majority of the ocean floor is underlain by relatively young, mafic oceanic crust, which is covered by modern sediments. A complex interplay between geological processes, related seafloor geomorphology, and a multitude of oceanographic processes controls the distribution of oceanic mineral deposit-forming environments in time and space. The most important deep ocean mineral deposits are ferromanganese crusts and nodules, and sulfide-rich deposits that are linked to submarine hydrothermal activity. Submarine hydrothermal systems are associated with magmatism and seafloor volcanism, which is principally concentrated along tectonic plate boundaries. In these environments circulation of seawater through the crust results in heating and chemical modification of the water to generate metal-rich hydrothermal fluids that may precipitate sulfide minerals at or below the seafloor. The resulting seafloor massive sulfide (SMS) deposits typically comprise a near-surface massive sulfide mound, underlain by sulfide-rich veins and disseminated mineralization. The chemical composition, morphology, rate of formation and size of SMS deposits varies as a function of geodynamic setting, the style of volcanism and tectonics, and water depth. Once an SMS deposit has accumulated on the seafloor it may be altered by a variety of hydrothermal, diagenetic and seafloor weathering and erosion processes. Geological understanding of the seafloor and the formation of SMS deposits is continuously evolving, and will help to focus ocean exploration in those areas likely to have the greatest mineral potential.

Oceanic hydrogenetic ferromanganese (Fe-Mn) crusts are a major repository for many metals, such as Co, Ni, Cu, Pt, Te and REE, which are essential for decarbonisation of transport and energy systems. Secondary mineralisation processes, occurring during phosphatisation episodes, commonly impregnate the shallower deposits with carbonate fluorapatite (CFA). The suboxic oceanic conditions during such events are frequently invoked to explain the lower Co content and unusually high Ni, Cu, Zn and Pt content of older phosphatised crusts. Here, the hypothesis of suboxic diagenetic recrystallization induced by phosphatisation episodes as a driving mechanism for Ni, Cu, Zn and Pt enrichment and Co depletion is evaluated. Accurately dated geochemical profiles, spanning 75 Ma of depositional history, for a shallow (1100 mbsl) phosphatised sample and a deeper (3100 mbsl) unphosphatised sample from Tropic Seamount in the north-east Atlantic, are compared. An isocon analysis, which allows to quantitively evaluate chemical gains and losses in mass transfer and therefore permits compensation for the dilution effect induced by the addition of CFA in the Fe-Mn crusts, demonstrates that no loss of Co has occurred in the phosphatised crust, whilst Pt, Te, Cu, Ni and Zn are enriched relative to younger, unphosphatised Fe-Mn crust. Both geochemical profiles show sympathetic trends and similar amplitudes of variation in concentration. This excludes phosphatisation as the driving mechanism for the metal enrichment and depletion. Systematic differences in metal content between the two samples, such as higher Cu and lower Co content in the deeper sample, are consistent with the depth profile of dissolved metal concentrations in the water column. The variability observed in the geochemical profiles is consistent with temporal changes in metal fluxes to the ocean, as a result of the evolving climate and oceanographic configuration of the north-east Atlantic Ocean through the Cenozoic. It is concluded that changing metal fluxes, rather than secondary mineralisation process associated with phosphatisation, is the dominant control on the primary metal content in Fe-Mn crust deposits at Tropic Seamount. (c) 2021 British Geological Survey, a component body of UKRI (BGS (c) UKRI ALL RIGHTS RESERVED. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The growth of ferromanganese (FeMn) crusts on soft substrates is uncommon. FeMn crusts generally accrete on hard-rock surfaces, where sedimentation rates are low and the rocks free of sediment cover. Here we use X-ray Powder Diffraction, Fourier Transform-Infra Red spectroscopy, Raman spectroscopy, X-ray Computed Micro Tomography, Scanning Electron Microscopy and Particle Size Distribution analysis to investigate FeMn crusts associated with a porous, weakly consolidated, and bioturbated siltstone consisting mainly of authigenic palygorskite. FeMn crusts occur both on the surface of the siltstone and as FeMn lining and/or infilling of bioturbation burrows. Our results show that variations in the water redox conditions lead to a micrometric alternation of hydro genetic vernadite and diagenetic todorokite and asbolane. These variations affected the oxidation state of Mn, which increased during the diagenetic formation of todorokite. The mineralogy of the FeMn oxides lining bioturbation traces is similar to that of the crusts growing on the siltstone, suggesting that they are genetically related and probably contemporaneous. Bioturbation burrows lined by FeMn oxides are unfilled (the siltstone porosity is 5-10%) or filled by bioclastic carbonate sediment. The soft siltstone possibly resulted from the alteration of volcaniclastic-pyroclastic sediments, forming authigenic palygorskite. Bioturbation of the sediment by burrowing organisms lead to seawater percolation, followed by hydrogenetic or diagenetic precipitation of FeMn linings under oxic/suboxic conditions within the burrows. These findings emphasize the importance of weakly-consolidated substrates with bioturbation cavities for the formation of marine polymetallic deposits.

Eight ferromanganese crust samples spanning the complete depth range of Tropic Seamount in the northeast Atlantic were analyzed for Pb and Nd isotopes to reconstruct water mass origin and mixing over the last 75 Ma. Pb isotopes were determined by laser ablation multicollector inductively coupled plasma mass spectrometer (LA‐MC‐ICP‐MS), which enables the rapid production of large, high spatial resolution data sets. This makes it possible to precisely correlate stratigraphy between different samples, compare contemporaneous layers, and create a composite record given the abundance of hiatuses in crusts. Pb and Nd isotope data show the influence of various oceanic and continental end‐members in the northeast Atlantic Ocean. This reflects its evolution from a restricted, isolated basins in the Late Cretaceous with influxes from the Tethys Ocean, to an increasingly well‐mixed, large‐scale basin, with a dominant Southern Ocean signature until the Miocene. Less radiogenic Nd isotope signatures suggest Labrador Sea Water influenced the northeast Atlantic basin as early as 17–15 Ma, flowing through a northern route such as the Charlie‐Gibbs Fracture Zone. Pb and Nd isotopes highlight the increasing influence of Saharan eolian dust input about 7 Ma, imparting a less radiogenic excursion to the binary mixing between North Atlantic water masses and riverine discharge from West and Central Africa. This highlights the influence of eolian dust input on the open ocean Pb and Nd budget and supports an early stage of North African aridification in the Late Miocene. This signature is overprinted about 3 Ma to the present by a strong North Atlantic Deep Water signature following the onset of Northern Hemisphere glaciation.

Hydrogenetic ferromanganese crusts are considered a faithful record of the isotopic composition of seawater influenced by weathering processes of continental masses. Given their ubiquitous presence in all oceans of the planet at depths of 400-7000 meters, they form one of the most well-distributed and accessible records of water-mass mixing and climate. However, their slow accumulation rate and poor age constraints have to date limited their use to explore 100 ka paleoclimatic phenomena. Here it is shown how the Pb isotope signature and major element content of a Fe-Mn crust from the north-east Atlantic responded to changes in the intensity and geographic extent of monsoonal rainfall over West Africa, as controlled by climatic precession during the Paleocene. The studied high-spatial resolution (4 mu m) laser-ablation multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICP-MS) Pb isotope data is a nearly 2 order of magnitude improvement in spatial and temporal resolution compared to micro-drill subsamples. The record demonstrates cyclicity of the (206)pb/(204)pb and (208, 207)pb/Pb-206 ratios at the scale of single Fe-Mn oxide laminae, in conjunction with variations in the Fe/Mn ratio, Al, Si and Ti content. Time-frequency analysis and astronomical tuning of the Pb isotope data demonstrates the imprint of climatic precession (similar to 20 ka) modulated by eccentricity (similar to 100 and 405 ka), yielding growth rates of 1.5-3.5 mm/Ma consistent with previous chemostratigraphic age models. In this context, boreal summer at the perihelion causes stronger insolation over West Africa, resulting in more intense and geographically extended monsoonal rainfalls compared to aphelion boreal summer conditions. This, in turn, influences the balance between the weathering endmembers feeding the north-east Atlantic basin. These results provide a new approach for calibrating Fe-Mn crust records to astronomical solutions, and allow their isotopic and chemical archive to be exploited with an improved temporal resolution of 1000-5000 years. (C) 2020 Copyright British Geological Survey (c) UKRI 2020. Published by Elsevier B.V.

Oceanic hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from ambient seawater over millions of years. Their very slow growth rates and physio-chemical properties mean that they adsorb numerous elements from seawater. As such, they provide condensed records of seawater evolution through time that can be used for paleoceanographic reconstruction. Here, we present the results of a high-resolution, stratigraphic, textural and geochemical investigation of a core sample, obtained from a Fe-Mn crust pavement, located on the summit of Tropic Seamount in the tropical north-east Atlantic Ocean. A number of observations and interpretations are proposed, within the context of a well-constrained age model, spanning the last 75 +/- 2 Myr. This core has textural stratigraphic coherence with Pacific Fe-Mn crusts formed since the Late Cretaceous, highlighting that global oceanic and climatic phenomena exert first-order controls on Fe-Mn crust development. All major hiatuses observed in the Fe-Mn crusts are contemporaneous with erosion events occurring throughout the Atlantic Ocean. High-resolution geochemical data indicate that there is variability in the composition of Fe-Mn crusts at the cm to mu m scale. The dominant factors controlling this include major oceanographic events, mineral textures and micro-topography.

Novel mineral prospectivity modelling presented here applies knowledge-driven feature extraction to a data-driven machine learning approach for tungsten mineralisation. The method emphasises the importance of appropriate model evaluation and develops a new Confidence Metric to generate spatially refined and robust exploration targets. The data-driven Random Forest™ algorithm is employed to model tungsten mineralisation in SW England using a range of geological, geochemical and geophysical evidence layers which include a depth to granite evidence layer. Two models are presented, one using standardised input variables and a second that implements fuzzy set theory as part of an augmented feature extraction step. The use of fuzzy data transformations mean feature extraction can incorporate some user-knowledge about the mineralisation into the model. The typically subjective approach is guided using the Receiver Operating Characteristics (ROC) curve tool where transformed data are compared to known training samples. The modelling is conducted using 34 known true positive samples with 10 sets of randomly generated true negative samples to test the random effect on the model. The two models have similar accuracy but show different spatial distributions when identifying highly prospective targets. Areal analysis shows that the fuzzy-transformed model is a better discriminator and highlights three areas of high prospectivity that were not previously known. The Confidence Metric, derived from model variance, is employed to further evaluate the models. The new metric is useful for refining exploration targets and highlighting the most robust areas for follow-up investigation. The fuzzy-transformed model is shown to contain larger areas of high model confidence compared to the model using standardised variables. Finally, legacy mining data, from drilling reports and mine descriptions, is used to further validate the fuzzy-transformed model and gauge the depth of potential deposits. Descriptions of mineralisation corroborate that the targets generated in these models could be undercover at depths of less than 300 ​m. In summary, the modelling workflow presented herein provides a novel integration of knowledge-driven feature extraction with data-driven machine learning modelling, while the newly derived Confidence Metric generates reliable mineral exploration targets.

Accurate age models for marine ferromanganese (Fe-Mn) crusts are essential to understand paleoceanographic changes and variations in local environmental factors affecting crust growth rate and their lateral continuity. However, no absolute method exists for dating these deposits beyond the age of 10 Myr, which requires the combination of a number of approaches. Here, we present a composite age model for a 15 cm thick Fe-Mn crust sample obtained by unique core drilling using a remotely operated vehicle at a water depth of 1130 m, on the summit of Tropic Seamount, in the north-east Atlantic. The age model is based on cross-validation of laser-ablation U-Pb dating, Co-chronometry and Os isotopes. These enable robust calibration of the age-depth model using the Bayesian statistical modelling of Markov Chain Monte Carlo (MCMC) simulations. The results show that this Fe-Mn crust commenced growth in the Late Cretaceous between 73 and 77 Ma, and grew at a rate between 1 and 24 mm/Myr, averaging 4 mm/Myr. The phosphatised carbonate substrate, capping Tropic Seamount and underlying most of the Fe-Mn crusts, yields a U-Pb age of 84 +/- 4 Myr, and provides the upper age limit for the model. Less radiogenic excursions of Os-188/Os-187 in the vertical profile through the crust permit the identification of key inflection points in the Os isotope seawater curve at the Eocene-Oligocene and Cretaceous-Paleogene transitions. Growth rates estimated from the empirical Co-chronometer are combined with the age envelope defined by the Os data and used to validate the MCMC simulations. The model identifies five hiatuses that occurred during the Pliocene (2.5 +/- 1.9-5.3 +/- 1.7 Ma), Early Miocene (16 +/- 1-27 +/- 2 Ma), Oligocene (29 +/- 2-32 +/- 1 Ma), Eocene (41 +/- 2-52 +/- 0.6 Ma), and the Late Paleocene (55 +/- 1-59 +/- 1.4 Ma). A major phosphatisation event affecting the Fe-Mn core can be dated to the Late Eocene (38 +/- 1.2 Ma), which coincides with a recorded change in the global oceanic system, from warm and sluggish circulation to cold and vigorous thermohaline-driven meridional overturn at the onset of Antarctic glaciation.

•Generic geological model of hydrothermally extinct seafloor massive sulphide.•Sub-surface characterisation by combined drilling and geophysics.•New sulphide resource estimate for slow-spreading mid-ocean ridges.•Holistic approach to assessing seafloor massive sulphide deposits.

The future extraction of deep-ocean mineral deposits depends on being able to recover the metals in an economic and environmentally sensitive way. Metal production is one of the most energy intensive industrial sectors. The characteristics of some deep-ocean mineral deposits permit them to be readily dissolved and to release their contained metals into solution. Current innovations in hydrometallurgy, including metal leaching with ionic liquids and solvent extraction in non-dispersive phase contactors, demonstrate how metals could potentially be extracted from Fe-Mn deposits with increased energy efficiency and a reduced environmental footprint compared with traditional processing techniques. The importance of biological processes in the formation of deep-ocean Fe-Mn deposits is poorly understood. However, understanding how microorganisms select and deposit metal ions could further enhance targeted extraction of 'critical' metals.

Over the last decade there has been an increasing interest in deep-sea mineral resources that may contribute to future raw metal supply. However, before seafloor massive sulfides (SMS) can be considered as a resource, alteration and weathering processes that may affect their metal tenor have to be fully understood. This knowledge cannot be obtained by assessing the surface exposures alone. Seafloor drilling is required to gain information about the third dimension. In 2016, three extinct seafloor massive sulfide mounds, located in the Trans-Atlantic Geotraverse (TAG) hydrothermal area of the Mid-Atlantic Ridge were drilled. A mineralogical and textural comparison of drill core and surface-grab samples revealed that in recent ceased mounds high-temperature copper assemblages typical for black smoker chimneys are still present whereas in longer extinct mounds the mineralogy is pre-dominated by an iron mineral assemblage. Zinc becomes remobilized early in the mound evolution and forms either a layer in the upper part of the mound or has been totally leached from its interior. Precipitation temperatures of sphalerite calculated using the Fe/Zn ratio can help to identify these remobilization processes. While the Fe/Zn ratios of primary sphalerites yield temperatures that are in very good agreement with fluid temperatures measured in white smokers, calculated temperatures for sphalerites affected by remobilization are too high for SMS. Overall drilling of SMS provides valuable information on the internal structure and mineralogy of the shallow sub-surface, however, additional drilling of SMS, at a greater depth, is required to fully understand the processes affecting SMS and their economic potential.

The Republic of Liberia in West Africa is underlain mostly by Precambrian rocks of Archaean (Liberian) age in the west and of Proterozoic (Eburnean) age in the east. By analogy with similar terranes elsewhere in the world, and in West Africa in particular, the geology of Liberia is favourable for the occurrence of deposits of a wide range of metals and industrial minerals, including gold, iron ore, diamonds, base metals, bauxite, manganese, fluorspar, kyanite and phosphate. Known gold deposits, mostly orogenic in style, occur widely and are commonly associated with north-east trending regional shear zones. Gold mining commenced at the New Liberty deposit in western Liberia in 2015, while significant gold resources have also been identified at several other sites in both Archaean and Proterozoic terranes. Liberia has large resources of itabirite-type iron ores, most of which are located in the Liberian terrane, and was the largest producer in Africa prior to the onset of civil war in 1989. Production of iron ore is currently restricted to a single mine, Yekepa, in the Nimba Range. Other important deposits, some of them previously mined, include Bong, the Western Cluster, Putu and Goe Fantro. There is a long history of alluvial diamond production in western and central Liberia, together with more than 160 known occurrences of kimberlite. Most of the known kimberlites occur in three clusters of small pipes and abundant dykes, located at Kumgbor, Mano Godua and Weasua, close to the border with Sierra Leone. Many of these are considered to be part of a single province that includes Jurassic age diamondiferous kimberlites in Sierra Leone and Guinea. Deposits and occurrences of a wide range of other metals and industrial minerals are also known. Several of these have been worked on a small scale in the past, mainly by artisanal miners, but most are poorly known in detail with sub-surface information available at only a few localities. By comparison with most other countries in West Africa, the geology of Liberia is poorly known and there has been very little systematic exploration carried out for most commodities other than gold, iron ore and diamonds since the 1960s and 1970s. Further detailed field and laboratory investigations using modern techniques are required to properly evaluate the potential for the occurrence of economic deposits of many minerals and metals in a variety of geological settings. Digital geological, geochemical, geophysical and mineral occurrence datasets, including new national airborne geophysical survey data, provide a sound basis for the identification of new exploration targets, but in almost every part of the country there is a need for new and more detailed geological surveys to underpin mineral exploration.

Regional lineament detection for mapping of geological structure can provide crucial information for mineral exploration. Manual methods of lineament detection are time consuming, subjective and unreliable. The use of semi-automated methods reduces the subjectivity through applying a standardised method of searching. Object-Based Image Analysis (OBIA) has become a mainstream technique for landcover classification, however, the use of OBIA methods for lineament detection is still relatively under-utilised. The Southwest England region is covered by high-resolution airborne geophysics and LiDAR data that provide an excellent opportunity to demonstrate the power of OBIA methods for lineament detection. Herein, two complementary but stand-alone OBIA methods for lineament detection are presented which both enable semi-automatic regional lineament mapping. Furthermore, these methods have been developed to integrate multiple datasets to create a composite lineament network. The top-down method uses threshold segmentation and sub-levels to create objects, whereas the bottom-up method segments the whole image before merging objects and refining these through a border assessment. Overall lineament lengths are longest when using the top-down method which also provides detailed metadata on the source dataset of the lineament. The bottom-up method is more objective and computationally efficient and only requires user knowledge to classify lineaments into major and minor groups. Both OBIA methods create a similar network of lineaments indicating that semi-automatic techniques are robust and consistent. The integration of multiple datasets from different types of spatial data to create a comprehensive, composite lineament network is an important development and demonstrates the suitability of OBIA methods for enhancing lineament detection.

The decarbonisation of our energy supply is reliant on new technologies that are raw material intensive and will require a significant increase in the production of metals to sustain them. Ferromanganese (FeMn) crusts are seafloor precipitates, enriched in metals such as cobalt and tellurium, both of which have a predicted future demand above current production rates. In this study, we investigate the texture and composition of FeMn crusts on Tropic Seamount, a typical Atlantic guyot off the coast of western Africa, as a basis for assessing the future mineral resource potential of Atlantic Seamounts. The majority of the summit is flat and covered by FeMn crusts with average thicknesses of 3–4 cm. The crusts are characterized by two dominant textures consisting of either massive pillared growth or more chaotic, cuspate sections of FeMn oxides, with an increased proportion of detrital and organic material. The Fe, Mn, and Co contents in the FeMn oxide layers are not affected by texture. However, detrital material and bioclasts can form about 50% of cuspate areas, and the dilution effect of this entrained material considerably reduces the Fe, Mn, and Co concentrations if the bulk samples are analyzed. Whilst Tropic Seamount meets many of the prerequisites for a crust mining area, the thickness of the crusts and their average metal composition means extraction is unlikely to be viable in the near future. The ability to exploit more difficult terrains or multiple, closely spaced edifices would make economic feasibility more likely.